There are so many types of combat that most people with find a nice preferred niche some where in combat space. The following are the basic positions in fleet combat. Smaller scale combat requires less people to perform these same jobs.

Note: The required skills noted here are only to use the modules required to perform that specific function, recommended requirements are skills that (on top of core skills) will improve your performance in that function.

The Tackler

Other MMO equivalent: Crowd Control
The individual tasked with keeping an enemy from escaping. A tackler's purpose is slow the target, make him unable to warp, disable microwarp and generally making the target unable to escape or effectively maneuver.

The Drainer (Supplementary Job)

Other MMO equivalent: Debuff
Capacitor power is life, and a Drainer removes that power from the enemy. Without capacitor power ships lose the ability to attack, repair and actively protect themselves leaving them vulnerable.

Skill Requirements:
Energy Emission Systems

The Damage Dealer

Other MMO equivalent: DPS
A damage dealer give maximum unadulterated damage to the target shredding through any protection through shear destructive power.

Skill Requirements:
[Skill for use of the weapon type of choice (and it's prerequisites) such as Medium Hybrid Turrets]

The Tanker

Other MMO equivalent: Tank
A tank wades through the massive damage keeping targets occupied to allow other weaker ships to disable and destroy the enemy.

Skill Requirements Although not technically required the following is necessary to prevent weaknesses that will cause an individual to be a bad tank:
Shield Tanks:
- Shield Upgrades
Armor Tanks:
- Hull Upgrades